Particulate property modifiers (e.g., fillers, opacifiers, pigments, reinforcements, fire retardants, etc.) are commonly used in polymer compositions. Prior to incorporating a particulate property modifier in a polymer composition, the particulate property modifier can be surface treated in order to increase the hydrophobicity of the property modifier. Increasing the hydrophobicity of the property modifier generally improves the dispersibility of the material in the polymer composition and increases the strength of the bond formed between the property modifier and the polymer matrix. As a result, (a) the particulate property modifier is more easily incorporated in the polymer composition, (b) a greater amount of the particulate property modifier can be incorporated in the polymer composition, and/or (c) the overall strength of the resulting polymer product is increased.
In one method commonly used for increasing the hydrophobicity of particulate property modifiers, the surface of a material is reacted with a silicon or titanium alkoxide coupling agent. Silicon and titanium alkoxides have been used successfully to treat numerous types of particulate materials. However, silicon and titanium alkoxides are relatively expensive and, therefore, are typically used only in special applications.
In another method commonly used for increasing the hydrophobicity of particulate pigmentary materials, a hydrous metal oxide (e.g., a hydrous oxide of aluminum, zinc, titanium, zirconium, or magnesium) is first precipitated on the surface of a particulate pigmentary material. Next, a surfactant (e.g., a saturated or unsaturated long-chained fatty acid or acid salt, a long-chained alcohol, a polyalcohol, dimethylpolysiloxane, or polyethylhydrosiloxane) is adsorbed on the hydrous metal oxide whereby the hydrophobicity of the particulate material is substantially improved. Unfortunately, however, the hydrous metal oxide precipitation step of this treatment method is typically a very lengthy process.
In their book entitled "Flotation," American Institute of Mining, Metallurgical and Petroleum Engineers, Inc., N.Y. 1976, pp. 148-196, M. C. Fuerstenau and B. R. Palmer discuss the anionic flotation of mineral oxides and silicates. Anionic collectors disclosed as useful for the flotation of mineral oxides and silicates include carboxylates (fatty acids), sulfonates, alkyl sulfates, and certain chelating agents. Collector adsorption may occur by electrostatic attraction to the mineral surface, by association of the collector, or by the chemical interaction of the collector with metal ions comprising the mineral surface. Metal ions comprising the mineral surface can include specifically adsorbed ions. Examples of specifically adsorbed ions include polyvalent metal ions in a pH region in which the metal ions hydrolyze to form hydroxy complexes. Fuerstenau and Palmer also suggest, based on experimental evidence, that collector adsorption in chemisorption systems can involve: (1) slight dissolution of the mineral followed by hydrolysis of metal ions contained in the dissolved mineral material, (2) adsorption of the resulting metal ion hydroxy complexes on the mineral surface by either hydrogen bonding or water formation, and (3) collector adsorption on the resulting metal ion sites. Fuerstenau and Palmer further suggest that, in the case of quartz, flotation is obtained only after metal ions are added to the system in a pH range within which the hydrolysis of the metal ions to their first hydroxy complex occurs.
Japanese Patent 2-279791 discloses a lubricant composite having a surface treated sericite material dispersed therein. The lubricant composite is formed by a method comprising the steps of: (a) suspending ultrafine particles of sericite in water and then adjusting the pH of the suspension to a value in the range of from 7 to 12; (b) adding an alkaline earth metal salt to the suspension so that alkaline earth metal ions are adsorbed on the surface of the sericite; (c) treating the resulting suspension with an anionic surfactant so that an adsorption film composed of the anionic surfactant is formed on the surface of the sericite; (d) drying the sericite; and (e) blending the dried sericite product with a nonionic surfactant and a carrier oil.